Laptop operation for the outwardly mobile

Many laptop (notebook) computers require a power supply having an output of between 14V and 23V. This makes it difficult to operate them from a car battery or other 12V source. One method would be to use a mains inverter 9 to give 230V a.c from the 12V d.c input) then connect this to the mains power adaptor supplied with the computer. However, not everyone has an inverter and if this were to be its only use, buying one would be hardly worthwhile. Also, it would be clumsy, bulky method and the efficiency of the arrangment would be low due to the losses at each stage.

The more elegant solution described here involves the use of a "boost switching regulator". This provides the necessary increase in d.c. voltage and stabilizes the output so that it remains substantially constant despite changes in load and/or input voltage. The finished device is fairly efficent operating at between 83 per cent (at maximum power output) and 90 per cent (under a light load)